1. Preheat your oven to 375°F (190°C). This temperature ensures a perfect golden finish without drying out the eggs.
2. Cook the bacon in a large, oven-safe skillet over medium heat until crispy, about 6-8 minutes. Remove the bacon and set it aside on a paper towel-lined plate to drain. Reserve 1 tablespoon of the bacon fat in the pan.
3. Add the olive oil and butter to the skillet with the bacon fat. Once melted, add the sliced potatoes and chopped onion. Season with a pinch of salt and pepper. Cook, stirring occasionally, until the potatoes are tender and beginning to brown, about 10-12 minutes. This step always reminds me of my grandmother’s kitchen, where patience was key—never rush the potatoes; the texture makes all the difference.
4. While the potatoes cook, whisk the eggs and milk together in a large bowl until combined. Stir in the grated cheese and crumble the cooked bacon.
5. Pour the egg mixture evenly over the potatoes and onions in the skillet. Let it cook without stirring for about 3-4 minutes on the stovetop until the edges start to set.
6. Transfer the skillet to the preheated oven and bake for 12-15 minutes, or until the frittata is puffed and golden on top, and a knife inserted in the center comes out clean.
7. Remove from the oven and let it rest for 5 minutes before slicing. Sprinkle with fresh chives or parsley for a pop of color and freshness.

I always find that letting the frittata rest helps the flavors settle and makes it easier to cut clean slices—something my kids appreciate when they’re eager to dig in!